Circuit Description

The oxygen sensor mounted in exhaust manifold monitors exhaust gas oxygen content and delivers an input signal to ECM. The ECM uses input signal to determine fuel injection system operation. Code is set when front oxygen sensor signal voltage is reduced to .35-.70 volt for 60 seconds under the following conditions:

• Engine coolant temperature is 176°F (80°C) or greater.
• Engine speed of 1900 RPM or greater.
• Driving under load, A/C on, flat surface at 60 MPH or less.
• Front oxygen sensor signal voltage is alternating between .35-.70 volt.